CHAP. VII MARSUPIALIA----POUCH 123 on the whole in the Polyprotodorit forms, such as the Thylacine, Dasyures, etc., but is found in so many of them that the two divisions of the Marsupials, the Diprotodonts and the Poly- pro todonts, cannot be raised to distinct orders on this and other grounds. The marsupial pouch of the Marsupials must not, as has been already pointed out, be confounded with the pouch of the Fia. 59.óBock Wallaby (Petrogale xanthopits}, -with young in pouch. x 3. (After Vogt and Speclit.) Monotreme mammals. Distinct teats are found in the iiiarsupium of the Marsupials, while there are none in the mammary pouch of the Monotreme, the pouch Itself indeed representing an un- differentiated teat, of which the walls have not closed up. The pouch opens forward in the KangaroOvS, and backwards in the Phfilaiigers and in the Polyprotodonts. Its walls are supported, by a pair of bones diverging from each other in a V-shaped manner; these are cartilaginous and vestigial in the Tbylaciiie.